Sheet separating device for an image input/output apparatus

ABSTRACT

A sheet separating device for an image input/output apparatus includes a ADF roller, a multi-layer pad and a spring. The spring forces elastically the multi-layer pad to contact the surface of the ADF roller. The multi-layer pad is composed of a first pad layer and a second pad layer superposed on the first pad layer in a stepped condition, and the second pad layer contacts the ADF roller in a pressed-over way. In separating sheets, the first pad layer and the second pad layer respectively separate sheets for two stages of action so that the probability of single sheet picking may be increased greatly. The first stage and the second stage of sheet separation are sequent and successive, not affecting the speed of sheet movement or the time needed for scanning or printing an image.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a sheet separating device, particularly to one applied to an auto document feeder installed with an image input/output apparatus employed in a scanner, a copier, a multi-functional product or a printer, for feeding papers placed in a paper tray into the image input/output apparatus for images capturing or performing. The sheet separating device has a function of single-sheet feeding and multiple sequent stages of sheet separating action.

2. Description of the Prior Art

One method of scanning by an image-scanning device is to place the document to be scanned on a scanning window and then to scan the document by means of an optical module for capturing an image of the document. Another method of scanning is to place the document in a paper tray then move the document and the optical module relatively by means of the auto document feeder with the optical module being in a stationary state for getting an image of the document. The auto document feeder has a sheet-separating device that can feed sheets one by one into the auto document feeder. The sheet-separating device includes a roller assembly consisting of plural rollers, and paper path formed by the rollers.

As for a printer, it also uses a sheet-separating device for feeding a sheet into the auto document feeder then print the image on the sheet.

As shown in FIGS. 1 and 2, the sheet-separating device mentioned above includes an ADF roller 12, a pad 14 and an elasticity element 16. The elasticity provide for elastic force to the pad 14 so that the pad 14 can to bias against the surface of the ADF roller 12.

During the operation, a plurality of sheet 18 placed in a paper tray (not shown), and one end of the sheet 18 is located between the ADF roller 12 and the pad 14. Then the sheet 18 is moved one by one by the ADF roller 12.

However, it is found in practical use that plural sheets may be picked up and moved into the sheet feeder 10, especially this may more easily happen in case of the sheet separating angle (θ shown in the FIG. 2) is too small, or large-weight-paper (such as mat finished coated paper) are used. The reason causes that is both the thickness and coefficient of friction of the sheets are different.

The problem of multiple feed can be improved by adjusting the sheet-separating angle, in addition to multiple stages of sheet separating action. The current technique is to use plural stages of sheet separating action so that the sheet-separating device may enhance the probability of picking up and feeding only a single sheet at one time.

SUMMARY OF THE INVENTION

The different friction of the ADF roller, documents and the friction pad is used to separate the documents. For further description, when the friction of the ADF roller and document is larger than the one of the documents or the document and pad, the ADF feed the document to be scanned.

The first purpose of the invention is to offer a sheet-separating device making sheet separating action for plural stages at one time, at least two stages, so the probability of single sheet feeding may be enhanced greatly, not affecting scanning function and the speed of sheet feeding.

The second purpose of the invention is to offer a sheet-separating device having a simple and compact structure, very convenient for assemblage and manufacture.

The sheet-separating device includes an ADF roller, a multi-layer pad and an elasticity element. The ADF roller is located at the sheet-feed end of a sheet feeder. The multi-layer pad is assembled on the housing of the sheet feeder and opposite to the ADF roller, which includes a first pad layer and a second pad layer. The elastic force of the elasticity element pushes the multi-pad forward to the ADF roller, so as to occur pressed-over between the second pad layer and the ADF roller.

When at least one of documents pass through the ADF roller and multi-pad, the ADF roller cooperates with the second pad layer to separate documents again. Therefore only single document is fed into the paper path of the automatic feeder device, wherein the paper path is formed by a plurality of rollers.

BRIEF DESCRIPTION OF DRAWINGS

This invention will be better understood by referring to the accompanying drawings, wherein:

FIG. 1 is a perspective view of a conventional sheet-separating device;

FIG. 2 is a cross-sectional view of the conventional sheet-separating device under an operating condition;

FIG. 3 is a perspective view of a first embodiment of a sheet-separating device in the present invention;

FIG. 4 is a cross-sectional view of the first embodiment of a sheet-separating device under an operating condition in the present invention;

FIG. 5 is a cross-sectional view of the first embodiment of a sheet-separating device under a stage of practically used condition in the present invention;

FIG. 6 is a cross-sectional view of the first embodiment of a sheet separating device under another stage of practically used condition in the present invention; and,

FIG. 7 is a cross-sectional view of a second embodiment of a sheet-separating device under a stage of practically used condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first preferred embodiment of a sheet separating device is applied to an auto document feeder, which includes the sheet separating device and a roller unit consisting of plural rollers. The roller unit faces to an end of the sheet separating device where a sheet comes out, forming a paper path for the sheet feeding out of the sheet-separating device to be moved thereon. The auto document feeder can be installed in an image input/output apparatus of a scanner, a printer, a copier or a multi-function product.

Please refer to the FIGS. 3 and 4. A sheet-separating device 30 in the present invention includes a ADF roller 40, a multi-layer pad 50, a mylar 60 and a spring 70, located at a sheet exit end of a paper tray arranged in an image input/output device.

The ADF roller 40 has an axial rotary shaft 42 for rotating the ADF roller 40.

The multi-layer pad 50 is located near the surface of the ADF roller 40, elastically pushed by the spring 70 to the ADF roller 40. Further, the multi-layer pad 50 is pushed to form an angle called as a sheet separating angle θ against the surface where the spring 70 stands on.

The mylar 60 is attached on the upper surface of the multi-layer pad 50, facing to the ADF pad 40.

The multi-layer pad 50 is composed of a first pad layer 52 and a second pad layer 54 superposed on the first pad layer 52, as shown in FIG. 4. The first and the second pad layer 52 and 54 may be made of the same material or different materials.

As the second pad layer 54 is located between the first pad layer 52 and the ADF roller 40, the ADF roller 40 may contact the second pad layer 54 in a pressed-over way after the sheet-separating device is assembled together, with the first pad layer 52 kept in normal contact with the surface of the ADF roller 40.

Next, as shown in FIG. 7, the second pad layer 54 of the multi-layer pad 50 may be made to have a first saw-tooth member 56 and a second saw-tooth member 58 formed at its front end for increasing friction against paper sheets so as to enhance sheet-separating effect. The first saw-tooth member 56, the second saw-tooth member 58 and the first pad layer 52 all contact with the ADF roller 40, and it should be noticed that the second saw-tooth member 58 of the second pad layer 54 is in contact with the ADF roller 40 in a pressed-over way Moreover, the first pad layer 52 and the second pad layer 54 may be independent from each other, or the first pad layer 52 and the second pad layer 54 may be integrated as one unit. The multi-layer pad 50 is also possible to consist of more than two pad layers superposed on one another, and the pad layer located farthest from the spring 70 is to be in contact with the ADF roller 40 in a pressed-over way.

Next, as shown in FIGS. 5 and 6, the ADF roller 40 should be rotated during performing automatic sheet-separation. Preferably, the bottom sheet 18 of papers piled up is to be picked up by the ADF roller 40 to move towards the exit end 32 of the sheet-separating device 30, and the sheet 18 is to be moved on a plural roller unit (not shown) at the exit end 32 and then enters the interior of an automatic sheet feeder. The second pad layer 54 cooperates with the ADF roller 40 for moving many sheets at the same time, and the piled-up sheets are separated for a second time by means of the first pad layer 52 and the ADF roller 40.

As the second pad layer 54 contacts with the ADF roller 40 in a pressed-over way, the bottom sheet of the piled-up papers receives comparative large force of the ADF roller 40 and is picked up first, so the probability of picking a single sheet at the first time may be enhanced in sheet separating action. In case plural sheets should be picked up at the first time of sheet separating, the second time of sheet picking by the action of the ADF roller 40 together with the first pad layer 52 can carry out single sheet separating for a second time, separating the plural sheets picked up by the first time, so the frequency of sheet separating action is increased for ensuring a single sheet separation at one round always.

The invention has the following advantages, as can be understood by the foresaid description.

1. Two or more pad layers are used in a multi-layer pad for friction, very simple in its structure, and very easy for assemblage or manufacture.

2. It has plural stages of sheet separating action at one time, possible to reduce the low miss feed probability that a conventional sheet-separating device has. For example, if a conventional sheet separating device has a miss percentage 5%, the miss percentage made by the two-stage separating device in the present invention will become 0.25% (5%×5%), surely enhancing the probability of single sheet separation.

3. The sheet separating in the present invention is sequent and continual, not slowing down the speed of the sheet feeding, or affecting the time for scanning or printing an image.

While the preferred embodiment of the invention has been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications that may fall within the spirit and scope of the invention. 

1. A sheet-separating device for an image input/output apparatus, said sheet-separating device disposed in a sheet feeder for feeding papers one sheet by one sheet, said sheet-separating device comprising; a ADF roller combined rotatably in said sheet feeder; a multi-layer pad fixed in a body of said sheet feeder and facing to said ADF roller, said multi-layer pad composed of at least a first pad layer and a second pad layer superposed on said first pad layer in a stepped condition; an elasticity element for pushing elastically said multi-layer pad to bias against said ADF roller; and, said second pad layer of said multi-layer pad contacting said ADF roller in a pressed-over way.
 2. The sheet separating device as claimed in claim 1, wherein said first pad layer and said second pad layer are made of different materials.
 3. The sheet separating device as claimed in claim 1, wherein said first pad layer and said second pad layer are made of the same material.
 4. The sheet separating device as claimed in claim 1, wherein a mylar is further provided to be attached on said second pad layer to contact said ADF roller.
 5. The sheet separating device as claimed in claim 1, wherein said first pad layer and said second pad layer are formed as integral as one unit in a stepped condition.
 6. The sheet separating device as claimed in claim 1, wherein said second pas layer has a saw shape formed in its front end contacting said ADF roller.
 7. The sheet separating device as claimed in claim 1, wherein said spring is posited between the multi-layer pad and a body of said auto sheet feeder. 